1. Field of the Invention
The present invention relates to a color correction apparatus and method for color correction. More particularly, the present invention relates to an apparatus and method for ambient light adaptive color correction.
2. Description of the Related Art
The application of digital projector has been expanded rapidly in the past few years. In particular, the development of LCD (Liquid Crystal Display) and DLP (Digital Light Processing) technology enables manufacturers produce projectors which are portable for not only business use but also personal home theatre. The typical visual environment for conventional projector is to project images on a projection plane in a dark room. As its application being widened, the demand for using projectors in normal light conditions such as office working environment and sunlight rays is growing more and more. Therefore, good color reproduction performance of a projector with consideration of ambient light effects is highly desired.
Japanese Patent No. 2973477 discloses a conventional projector, which detects the color and brightness of the projection planes and adjusts the white balance and brightness based on the detected color and brightness information. Therefore, the color reproduction is achieved by matching reproduced color to the target color values calorimetrically without consideration of color appearance of images. However, since the human color perception is complicated and the color appearance is frequently affected by the view environment and white color, the color appearance matching of the whole image would be desired rather than simple colorimetrical matching method under different lighting environment.
Further, Japanese Patent Application Unexamined publication No. 2001-320725 discloses an environment adaptive projector invented by Seiko Epson Corp, which uses a color sensor to measure the color information such as RGB or XYZ values from the projection plane on which a white image is projected with the influence of ambient light. Then, a complementary color, which is output as a corrected color, can be generated in CIELAB color space. Such a color correction can be repeatedly performed for plural levels of grey and the results are stored in a gamma-correction lookup table.
However, the above adaptive projector cannot always obtain satisfactory color reproduction due to the following reasons: 1. Even if a complementary color to the white color is projected on a projection plane, its reproduced color on the projection plane is not always a grey or achromatic color because of “chromatic grey” phenomenon. 2. More importantly, as to colors other than achromatic colors, subjected to the color correction using the complementary color pair, it does not ensure that the color appearance of such color becomes desired color appearance. Therefore, it can't achieve color appearance matching under different illumination conditions.
As described above, the prior patents haven't provided a color correction method of achieving color appearance matching. Also, the above patents haven't taken the gamut mapping into consideration. However, in fact the displayable color gamut of the projector can be affected significantly under influence of different external lighting environment. Consequently, the color appearance of the obtained corrected images in lighting room can't be closed to that in the dark room and can't be satisfied either.